JP3556182B2 - Electric power steering device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device in which the power of an electric motor is applied to a steering system as a steering assist force to reduce a driver's steering force. More particularly, the present invention relates to an electric power steering device that improves a reduction in steering feeling due to a response delay in control of a steering system.
[0002]
[Prior art]
In a conventional electric power steering device, a steering torque generated by a driver operating a steering wheel is detected by a steering torque sensor, and the detected steering torque signal is converted into a target current signal for driving the electric motor. Generates a signal obtained by subjecting a deviation signal from a motor current signal corresponding to the actually flowing motor current to PI (proportional / integral) or PID (proportional / integral / differential) control, and generates a motor control signal based on this signal. 2. Description of the Related Art It is known that a motor is driven by (for example, a PWM signal) to apply a steering assist force to a steering system.
[0003]
In such a conventional electric power steering apparatus, since the motor current signal is fed back (negatively fed back) to the target current signal to perform PI control or PID control, the deviation signal is quickly controlled to be 0, and the motor current is controlled. Converges on the value set by the target current signal to drive the motor, and a steering assist force corresponding to the steering torque signal is obtained.
[0004]
FIG. 7 shows a block diagram of a main part of a conventional electric power steering apparatus.
FIG. 7 shows an example in which PI (proportional / integral) control is performed on the control system.
7, an electric power steering device 50 includes a steering torque sensor 12, a vehicle speed sensor 14, a control unit 51, a motor driving unit 16, a motor current detecting unit 18, and the motor 10.
[0005]
The control means 51 is composed of various arithmetic means, comparison / processing means, memory and the like based on a microprocessor, and includes a target current setting means 52, a deviation calculation means 53, a proportional / integral control means 54, and a control signal generation means 55.
[0006]
The steering torque sensor 12 detects a steering torque generated in response to a driver's steering operation as an analog electric signal, and a steering torque signal TS is supplied to the target current setting means 52.
The vehicle speed sensor 14 detects an electric pulse signal having a frequency corresponding to the speed of the vehicle, and the vehicle speed signal VS is supplied to the target current setting means 52.
[0007]
The target current setting means 52 converts the steering torque signal TS supplied from the steering torque sensor 12 into a digital steering torque signal TD, and based on the steering torque signal TD and the vehicle speed signal VS supplied from the vehicle speed sensor 14, The target current signal IMS corresponding to the steering torque signal TD using the vehicle speed VS (VL, VM, VH) as a parameter is output to the deviation calculating means 53.
[0008]
FIG. 8 shows a steering torque signal (TD) -target current signal (IMS) characteristic diagram (Table 1) using the vehicle speed as a parameter.
In FIG. 8, vehicle speeds VL, VM, and VH indicate a low vehicle speed region, a medium vehicle speed region, and a high vehicle speed region, respectively. Even when the steering torque signal TD is the same, the vehicle speed VS increases (VL → VM → VH). Accordingly, the target current signal IMS is preset so as to decrease.
[0009]
In this manner, the target current setting means 52 is configured to drive the motor 10 with a large motor current IM corresponding to the target current signal IMS in a low vehicle speed region (VS = VL) to obtain a sufficiently large steering assist force. On the other hand, in the high vehicle speed region (VS = VH), the motor 10 is driven by the small motor current IM corresponding to the target current signal IMS to suppress the steering assist force, and to obtain the steering stability.
[0010]
The deviation calculating means 53 calculates a deviation (= IMS-IMO) between the target current signal IMS and the motor current signal IMO detected by the motor current detecting means 18 and converted into a digital signal corresponding to the motor current IM. The deviation signal ΔI is provided to the proportional / integral control means 54.
[0011]
The proportional / integral control means 54 is constituted by connecting in parallel a proportional element for multiplying the deviation signal ΔI by the proportional sensitivity KP and an integral element for integrating and controlling the deviation signal ΔI (= IMS−IMO) with the integral gain KI. A proportional / integral operation is performed on ΔI, and a proportional / integral signal IPI is supplied to the control signal generating means 55.
The proportional / integral signal IPI is expressed by Equation 1 using the proportional sensitivity KP and the integral gain KI.
[0012]
(Equation 1)
IPI = KP * ΔI + (KI / p) * ΔI
Where p is a heaviside operator
[0013]
By setting the values of the proportional sensitivity KP and the integral gain KI to be large, the motor current signal IMO (corresponding to the motor current IM) can quickly converge on the target current signal IMS (deviation signal ΔI = 0).
[0014]
The control signal generating means 55 includes a PWM (pulse width modulation) signal generating means. A PWM signal VPWM corresponding to the magnitude and direction of the proportional / integral signal IPI is supplied to the motor driving means 16 as a motor control signal VO. The motor is driven by the motor voltage VM supplied from the motor driving means 16.
[0015]
The motor 10 is driven by the motor control signal VO and the motor current IM flows. The motor current detection means 18 detects the motor current IM, and the motor current signal IMO corresponding to the motor current IM is fed back to the deviation calculation means 53. Is done.
[0016]
As described above, the conventional electric power steering device 50 is configured to feed back (negative feedback) the motor current signal IMO corresponding to the motor current IM to the target current signal IMS and perform proportional / integral control on the deviation signal ΔI. In addition, the motor current signal IMO is quickly converged to the target current signal IMS, and motor power corresponding to the steering torque is obtained, so that a desired steering assist force with good responsiveness can be applied to the steering system.
[0017]
Further, since the conventional electric power steering device 50 is configured to perform the integral control on the deviation signal ΔI, the electric motor current signal IMO corresponding to the electric motor current IM is matched with the target current signal IMS, and the offset value is set to 0. be able to.
[0018]
[Problems to be solved by the invention]
When the steering assist force is large and the number of rotations of the electric motor 10 is high, as in the case of steering when the steering wheel is turned off or running at low speed, the conventional electric power steering device 50 includes an inductance component of the armature winding of the electric motor 10. The induced back electromotive force increases, the motor current IM flowing through the motor 10 decreases, and the deviation signal ΔI (= IMS−IMO) tends to have a large value.
[0019]
When the steering wheel is turned back for quick turning from such a steering wheel stationary state, the integral value (KI / p) * ΔI of the integral term represented by the second term of Expression 1 is large, and the target current signal IMS Is opposite to the sign of the target current signal IMS constituting the deviation signal ΔI (= IMS−IMO) of the integral value (KI / p) * ΔI, the delay time until the integral value once converges to 0 is long, Since a steering assist force in a direction opposite to the steering direction of the driver acts on the steering system, there is a problem that a sudden change is exerted on the steering holding force of the driver and the steering feeling is significantly reduced.
[0020]
The present invention has been made to solve such a problem, and an object of the present invention is to provide an electric power steering device that can obtain an optimum steering feeling even when the steering wheel is turned quickly for turning from a steering wheel stationary state. It is in.
[0021]
[Means for Solving the Problems]
In order to solve the above problems, an electric power steering device according to the present invention includes: It comprises limiting means and multiplying means, wherein the limiting means comprises: If the signal output from the integration element is equal to or less than a predetermined value, the signal is output as it is, and if the signal output from the integration element exceeds a predetermined value, the signal is output. The limiting coefficient is supplied to the multiplying means, and the integration signal output from the integrating element is limited to a predetermined value or less by the limiting coefficient. It is characterized by the following.
[0022]
Since the control means has a limiting means, if the signal output from the integration element is equal to or less than a predetermined value, the signal is output as it is, and if the signal output from the integration element exceeds a predetermined value, the signal is limited to a predetermined value or less. Even if the steering wheel is quickly turned back from the steering wheel stationary state, the response delay of the signal due to the integral element can be compensated.
[0023]
The limiting means according to the present invention includes a sign inversion detecting means for detecting the reversal of the steering direction, and an integral value comparing means for comparing the integral value of the integral element with a preset reference value. , And a signal output from the integration element based on a signal output from the integration value comparison means.
[0024]
Limiting means according to the present invention includes a sign reversal detecting means for detecting reversal of the steering direction, an integral value comparing means for comparing an integral value of the integral element with a preset reference value, and a sign reversing detecting means; Since the signal output from the integration element is limited based on the signal output from the integration value comparison means, it is possible to reliably detect the turning of the steering wheel which is fast turning from the steering wheel stationary state and compensate for the response delay of the signal due to the integration element. can do.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
According to the present invention, the signal output from the integral element of PI (proportional / integral) control constituting the control system is limited at the time of turning back the steering wheel from the stationary steering state to the fast steering, and the response delay of the signal by the integral element is restricted. In order to obtain an optimum steering feeling.
[0026]
FIG. 1 is an overall configuration diagram of an electric power steering device according to the present invention.
In FIG. 1, an electric power steering apparatus 1 includes a steering shaft 2 provided integrally with a steering wheel 17 and a connecting shaft 3 provided with universal joints 3a and 3b. The manual steering force generating means 6 is connected to the pinion 5 a of the pinion mechanism 5.
[0027]
The rack shaft 7 is provided with rack teeth 7a meshing with the pinion 5a. The left and right front wheels 9 as steering wheels are connected to both ends of the rack shaft 7 reciprocating by the meshing.
[0028]
Thus, when the steering wheel 17 is steered, the direction of the vehicle is changed by rolling the front wheels 9 by manual steering via the normal rack and pinion type manual steering force generating means 6.
[0029]
In order to reduce the steering force generated by the manual steering force generating means 6, an electric motor 10 for supplying a steering assist force is disposed coaxially with the rack shaft 7, and via a ball screw mechanism 11 provided coaxially with the rack shaft 7. It is converted into thrust and acts on the rack shaft 7 (ball screw shaft 11a).
[0030]
A steering torque sensor 12 for detecting the direction and magnitude of the driver's manual steering torque and a steering rotational speed sensor 13 for detecting the direction and magnitude of the steering rotational speed of the steering wheel 17 operated by the driver are provided in the steering gear box 4. And a steering torque signal TS of an analog electric signal corresponding to the steering torque detected by the steering torque sensor 12 and a steering rotational speed signal NS of an analog electric signal corresponding to the steering rotational speed detected by the steering rotational speed sensor 13, respectively. Is provided to the control means 15.
The vehicle speed sensor 14 detects an electric pulse signal having a frequency corresponding to the speed of the vehicle, and provides a vehicle speed signal VS to the control unit 15.
[0031]
Note that a motor rotation speed sensor may be provided instead of the steering rotation speed sensor 13 to calculate the steering rotation speed NS from Equation 2.
[0032]
(Equation 2)
NS = K1 (NM-dTS / dt)
Where K1 is a constant, NM is the motor rotation speed,
dTS / dt is the differential value of the steering torque TS
[0033]
Further, the motor rotation speed NS can be estimated from Expression 3 using the motor voltage VM, the motor current IM, the induced voltage coefficient KM of the motor, and the motor internal resistance RM.
[0034]
(Equation 3)
NS = (VM−RM * IM) / KM
[0035]
The control means 15 is composed of various arithmetic means, processing means, signal generation means, memory and the like based on a microprocessor, and outputs a motor control signal VO (for example, a mixed signal of an ON signal and a PWM signal) corresponding to the steering torque signal TS. The generated motor drive means 16 is driven and controlled.
[0036]
Further, the control means 15 includes a proportional / integral control means and a limiting means for limiting a signal output from the integral element of the proportional / integral control means. The signal is limited to compensate for the response delay of the signal due to the integration element.
[0037]
The motor driving unit 16 is configured by a bridge circuit including, for example, four power FET (field effect transistor) switching elements, and outputs the motor voltage VM based on the motor control signal VO to drive the motor 10.
[0038]
The motor current detecting means 18 detects the motor current IM actually flowing through the motor 10 and feeds back (negative feedback) a motor current signal IMO corresponding to the motor current IM to the control means 15.
[0039]
FIG. 2 is a block diagram of a main part of the electric power steering apparatus according to the present invention.
2, the control means 15 includes a target current setting means 21, a deviation calculating means 22, a proportional / integral control means 23, a control signal generating means 27, and a limiting means 30.
[0040]
Note that the target current setting means 21, deviation calculation means 22 and control signal generation means 27 have the same configuration and the same operation as the target current setting means 52, deviation calculation means 53 and control signal generation means 55 shown in FIG. Omitted.
[0041]
The proportional / integral control means 23 generates a proportional sensitivity KP to proportionally control the deviation signal ΔI (= IMS-IMO), and generates a integral gain KI to generate the deviation signal ΔI (= IMS-IMO). An integral element 25 for performing integral control, a multiplying means 28 for multiplying the output signal from the integral element 25 by a limiting coefficient KL, and an adding means 26 for adding the output signals of the proportional element 24 and the multiplying means 28 are provided.
[0042]
The integrating element 25 connected in series with the multiplying means 28 is connected in parallel with the proportional element 24. The proportional element 24 supplies to the adding means 26 a proportional signal IP obtained by multiplying the deviation signal ΔI by the proportional sensitivity KP.
The integration element 25 provides an integral signal (integral value) II obtained by subjecting the deviation signal ΔI to integral processing with an integral gain KI to the multiplying means 28, and the integral limiting signal IL (= II) obtained by multiplying the limiting signal KL by the multiplying means 28. × KL) is supplied to the adding means 26.
[0043]
The adding means 26 adds the proportional signal IP and the integral limiting signal IL (= II × KL) and outputs a proportional / integral signal IPI (= IP + IL) to the control signal generating means 27.
[0044]
The limiting means 30 includes a sign inversion detecting means, a rotational speed comparing means, an integral value comparing means, a limiting coefficient generating means, etc., and the steering rotational speed signal NS detected by the steering rotational speed sensor 13 and the integral signal supplied from the integral element 25. Based on the (integral value) II, the steering state at the time of turning back the steering wheel from the steering wheel stationary state to the fast steering is detected, and the limiting coefficient KL is supplied to the multiplying means 28.
[0045]
The multiplication means 28 multiplies the integral signal (integral value) II by the limiting coefficient KL to obtain an integral limiting signal IL (= II × KL) in which the integral signal (integral value) II is limited by the limiting coefficient KL. Thus, for example, the response delay due to the integral control of the integral element 25 can be improved by setting the limit coefficient KL to a value less than 1 (0 ≦ KL <1).
[0046]
The proportional / integral signal IPI (= IP + IL) output from the adding means 26 is converted by the control signal generating means 27 into a PWM signal VPWM corresponding to the magnitude and direction of the proportional / integral signal IPI (= IP + IL). VPWM is supplied to the motor drive means 16 as the motor control signal VO, and the motor 10 is driven by the generated motor voltage VM, and the power of the motor 10 acts on the steering system as steering assisting force.
[0047]
As described above, in the electric power steering apparatus 1 according to the present invention, the control unit 15 includes the limiting unit 30 to limit the integration signal (integral value) II output from the integration element 25 by the limiting coefficient KL. Even if the steering wheel is turned quickly for turning from the turning state, the proportional signal IP output from the proportional element 24 becomes dominant, and the response delay of the signal by the integrating element 25 can be compensated.
[0048]
FIG. 3 is a block diagram of a main part of the restricting means according to the present invention.
The limiting means 30 includes a sign inversion detecting means 31, a rotational speed comparing means 32, an integral value comparing means 33, a logical product calculating means 34, a level holding means 35, a limiting coefficient generating means 36, and a limiting stop control means 37. On the basis of the steering rotation speed signal NS detected by the speed sensor 13 and the integration signal (integral value) II supplied from the integration element 25 shown in FIG. A limiting coefficient KL for attenuating the signal (integral value) II is generated.
[0049]
The sign inversion detecting means 31 detects the rising or falling of the polarity of the steering rotation speed signal NS (for example, a polarity judging means (not shown), which is a binary signal of H level in the right direction of the steering wheel and L level in the left direction of the steering wheel). The polarity inversion is detected as a trigger, and every time the polarity inversion is detected, the polarity inversion signal HO including, for example, an H-level one-shot pulse is provided to the AND operation means 34.
[0050]
FIG. 4 is a block diagram showing a main part of an embodiment of the sign inversion detecting means according to the present invention.
In FIG. 4, the sign inversion detection means 31 includes a positive polarity inversion detection means 31A, a negative polarity inversion detection means 31B, and a logical sum operation means 31C.
[0051]
The positive polarity reversal detecting means 31A and the negative polarity reversing detecting means 31B are constituted by, for example, retriggerable mono-multi vibrators, and one-shot pulses (for example, for a predetermined time TM) triggered by rising and falling of the polarity of the steering rotation speed signal NS, respectively. A positive polarity detection signal Pτ + and a negative polarity detection signal Pτ− (H level) are supplied to the OR operation means 31C.
[0052]
The logical sum operation means 31C has a logical sum gate or a logical sum operation function, and has a positive polarity detection signal Pτ + supplied from the positive polarity inversion detection means 31A and a negative polarity detection signal Pτ supplied from the negative polarity inversion detection means 31B. The logical OR of-is calculated, and a polarity inversion signal HO (H-level one-shot pulse for a predetermined time TM) is output.
[0053]
The rotation speed comparison unit 32 includes a memory such as a ROM and a comparison unit, and compares the reference rotation speed NK preset in the memory with the steering rotation speed signal NS, and the steering rotation speed signal NS exceeds the reference rotation speed NK (NS > NK), a rotation speed determination signal NO of, for example, an H level is provided to the AND operation means 34.
Note that the rotation speed comparison means 32 can be omitted.
[0054]
As described above, the sign inversion detecting means 31 detects the turning of the steering wheel by detecting the polarity of the steering rotational speed signal NS, and the rotational speed detecting means 32 calculates the steering rotational speed signal NS from the comparison result between the steering rotational speed signal NS and the reference rotational speed NK. Since an abrupt turning operation of the steering wheel can be detected, it is possible to detect a turning operation of the steering wheel from a fast steering operation performed by the driver from a logical product of the polarity reversal signal HO and the rotation speed determination signal NO.
[0055]
The integrated value comparing means 33 includes a memory such as a ROM and a comparing means, and compares the reference integrated value IK preset in the memory with the integrated signal (integrated value) II. (II> IK), for example, an H level integrated value determination signal IO is provided to the AND operation means 34.
[0056]
In this way, by setting the reference integral value IK so as to correspond to the vicinity of the stationary steering wheel and detecting the integral value determination signal IO, the driver's stationary steering wheel operation can be detected.
[0057]
The AND operation means 34 has a three-input AND gate or an AND operation function, and calculates the logical AND of the polarity inversion signal HO, the rotation speed determination signal NO, and the integral value determination signal IO. When all of the rotation speed determination signal NO and the integral value determination signal IO are at the H level, the logical product data DO at the H level is provided to the level holding unit 35.
[0058]
Therefore, when the logical product data DO output from the logical product calculating means 34 is at the H level, it is possible to detect a state in which the steering wheel is turned from a stationary steering state to a fast turning state.
[0059]
The level holding means 35 has a latch function, holds the logical product data DO supplied from the logical product calculating means 34, and provides an H level holding signal LO to the limiting coefficient generating means 36, for example.
[0060]
The level holding unit 35 has a latch release function, releases the latch based on the stop control signal SC supplied from the limit stop control unit 37, and stops the holding signal LO supplied to the limit coefficient generation unit 36.
[0061]
The limiting coefficient generating means 36 is composed of a memory such as a ROM, a selecting means, and the like, and stores a plurality of limiting coefficients KL (for example, 1 and 0) preset in the memory based on a holding signal LO supplied from the level holding means 35. The selected limiting coefficient KL is provided to the multiplying means 28 shown in FIG.
[0062]
For example, when the hold signal LO is at the H level, the limit coefficient KL (= 0) is selected and output. On the other hand, when the hold signal LO is prohibited (for example, the hold signal LO is at the L level), the limit coefficient KL is selected. (= 1) is selected and output.
[0063]
FIG. 5 shows a characteristic diagram of the limiting coefficient KL of the limiting coefficient generating means according to the present invention.
In FIG. 5, the limit coefficient KL is set to 1 (KL = 1) in a region before time t1 and after time t2 corresponding to a normal steering state, and an integral signal (integral value) output from the integral element 25 is set. ) II is output to the adding means 26 as an integration limiting signal IL (= II) having the same value.
[0064]
On the other hand, in the region from the time t1 to the time t2, the limiting coefficient KL is set to 0 (KL = 0) corresponding to the steering state in which the steering wheel is turned from the steering wheel stationary state to the fast steering, and is output from the integration element 25. The integral signal (integral value) II is output to the adding means 26 as an integral limiting signal IL (= 0) limited by the limiting coefficient KL, and the response delay of the signal caused by the integral element 25 of the steering assist force acting on the steering system. Can be compensated for.
[0065]
The limit stop control means 37 has a comparator or a comparison function, compares the integral signal (integral value) II with a preset reference value IX, and the integral signal (integral value) II falls below the reference value IX (II <IX). In this case, for example, an H-level stop control signal SC is provided to the level holding unit 35, and control is performed to release the latch of the logical product data DO held by the level holding unit 35.
[0066]
As an embodiment of the present application, an example has been described in which the limit coefficient KL for the steering state in which the steering wheel is quickly turned from the steering wheel stationary state to the steering state is set to 0. The coefficient KL may be set to a predetermined value below 1 (0 <KL <1), and the integration limiting signal IL may be set to a constant value other than 0 (0 <IL <1).
[0067]
Further, as a simpler embodiment of the present invention, a limiting means 41 is provided between the integrating element 25 and the adding means 26 instead of the steering rotational speed sensor 13, the limiting means 30, and the multiplying means 28 in FIG. When the signal II exceeds a predetermined value IY (II> IY), the integrated signal II may be limited to the predetermined value IY and supplied to the adding means 26.
[0068]
FIG. 6 is a block diagram of a principal part of another embodiment of the proportional / integral control means according to the present invention.
6, the proportional / integral control means 40 differs from the proportional / integral control means 23 shown in FIG. 2 in that a limiting means 41 is provided between the integrating element 25 and the adding means 26 instead of the multiplying means 28.
[0069]
The limiting means 41 has a memory for storing a predetermined value IY of a preset integral value, and a comparing function. The limiting means 41 compares the integral signal (integral value) II supplied from the integrating element 25 with the predetermined value IY, and When the integrated value (II) is equal to or smaller than the predetermined value IY (II ≦ IY), the integrated signal (integrated value) II is output as it is to the adding means 26 as the integration limiting signal IL. When the value exceeds IY (II> IY), the integration signal (integral value) II is limited to a predetermined value IY and is output to the adding means 26 as the integration limiting signal IL.
[0070]
As described above, the electric power steering apparatus 1 according to the present invention according to the present invention includes, in the limiting means 30, the sign inversion detecting means 31, the rotational speed comparing means 32, the integral value comparing means 33, and the limiting coefficient generating means 36. Therefore, the steering wheel turning of the fast steering is reliably detected from the steering wheel stationary state, and the limit coefficient is generated, and the signal output from the integral element is corrected by the limit coefficient, so that the response delay of the signal due to the integral element is compensated. be able to.
[0071]
In addition, the limiting coefficient generating means 36 of the electric power steering apparatus 1 according to the present invention can generate a predetermined limiting coefficient and reduce the signal output from the integration element 25 to a constant value. Even if the steering wheel is turned back for a quick steering, the response delay of the signal by the integration element 25 can be compensated.
[0072]
【The invention's effect】
As described above, the electric power steering apparatus according to the present invention includes the limiting means in the control means, and when the signal output from the integration element is equal to or less than a predetermined value, outputs the signal as it is, and outputs the signal output from the integration element. When the steering wheel exceeds the predetermined value, the steering speed is limited to the predetermined value or less. Can compensate.
[0073]
Further, the limiting means according to the present invention includes a sign reversal detecting means for detecting reversal of the steering direction, and an integral value comparing means for comparing the integral value of the integral element with a preset reference value. , And the signal output from the integration element based on the signal output from the integration value comparison means, so that it is possible to reliably detect the turning of the steering wheel in a fast steering from the steering wheel stationary state and to delay the response of the signal by the integration element. And an optimum steering feeling can be secured.
[0074]
Therefore, it is possible to provide an electric power steering apparatus that can provide a stable steering feeling even when the steering wheel is turned quickly for turning from the steering wheel stationary state.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an electric power steering device according to the present invention.
FIG. 2 is a block diagram of a main part of an electric power steering apparatus according to the present invention.
FIG. 3 is a block diagram of a main part of a limiting unit according to the present invention.
FIG. 4 is a block diagram of a main part of an embodiment of a sign inversion detecting means according to the present invention;
FIG. 5 is a characteristic diagram of a limiting coefficient KL of the limiting coefficient generating means according to the present invention.
FIG. 6 is a block diagram showing a principal part of another embodiment of the proportional / integral control means according to the present invention;
FIG. 7 is a block diagram of a main part of a conventional electric power steering device.
FIG. 8 is a characteristic diagram of steering torque signal (TD) -target current signal (IMS) using vehicle speed as a parameter (Table 1).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering shaft, 3 ... Connecting shaft, 3a, 3b ... Universal joint, 4 ... Steering gear box, 5 ... Rack & pinion mechanism, 5a ... Pinion, 6 ... Manual steering force generating means, Reference numeral 7: rack shaft, 7a: rack teeth, 8: tie rods, 9: left and right front wheels, 10: electric motor, 11: ball screw mechanism, 12: steering torque sensor, 13: steering rotation speed sensor, 15: control means, 16 ... Motor driving means, 17 steering wheel, 18 motor current detecting means, 21 target current setting means, 22 deviation calculating means, 23, 40 proportional / integral control means, 24 proportional elements, 25 integrating elements, 26 ... adding means, 27 ... control signal generating means, 28 ... multiplying means, 30, 41 ... limiting means, 31 ... sign inversion detecting means, 31A ... positive polarity inversion detecting means, 3 B: negative polarity inversion detecting means, 31C: logical sum calculating means, 32: rotational speed comparing means, 33: integrated value comparing means, 34: logical product calculating means, 35: level holding means, 36: limiting coefficient generating means, 37 ... Limit stop control means, DO: Logical product data, HO: Polarity inversion signal, II: Integration signal (integral value), IK: Reference integral value, IL: Integration limit signal, IM: Motor current, IMO: Motor current signal, IMS: target current signal, IO: integral value determination signal, IP: proportional signal, IPI: proportional / integral signal, ΔI (= IMS-IMO): deviation signal, KI: integral gain, KL: limiting coefficient, KP: proportional sensitivity , LO: holding signal, NK: reference rotation speed, NO: rotation speed determination signal, NS: steering rotation speed signal, Pτ +: positive polarity detection signal, Pτ−: negative polarity detection signal, SC: stop control signal, TS: steering G Click signal, VPWM ... PWM signal, VM ... motor voltage, VO ... motor control signal.

Claims (1)

An electric motor for applying a steering assist force to a steering system, target current setting means for determining a target current signal for driving the electric motor based on a steering torque signal from a steering torque sensor, and a target current signal from the target current setting means And a control means comprising a proportional / integral control means having at least a proportional element and an integral element for performing proportional control and integral control on the deviation of the motor current signal from the motor current detection means, and an output from the proportional / integral control means. Motor driving means for driving the motor based on the electric power steering device,
The control unit includes a limiting unit and a multiplying unit,
When the signal output from the integration element is equal to or less than a predetermined value, the limiting means outputs the signal as it is, and when the signal output from the integration element exceeds a predetermined value, supplies a limiting coefficient to the multiplication means. Limiting the integration signal output from the integration element to a predetermined value or less with the limiting coefficient,
Further, the limiting means includes a sign inversion detecting means for detecting a reversal of a steering direction, and an integral value comparing means for comparing an integral value of the integral element with a preset reference value, and the sign inversion detecting means, And an electric power steering device for limiting a signal output from the integration element based on a signal output from the integration value comparison means .

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